Rotary kiln drive mechanism



Oct. 27, 1959 J. c. HOLM 2,910,286 y f ROTARY KI'LN DRIVE MECHANISM Filed 001;. 27, 1955 2 Sheets-Sheet 1 IN V EN TOR. 01m

1 9 ROTARY KILN DRIVE MECHANISM Tens C. Holm, Evanston, Ill., assignor to Marland One- Way Clutch Co., La Grange, Ill.

I The present invention relates to rotary kilns and mechanisms for rotating a rotary kiln. More particularly, the present invention relates to mechanisms for rotating rotary kilns, such 'as those used in a cement and other manufacturing processes. 1

' The process generally used in manufacturing cement employs a rotary kiln of considerable length, usually disposed on an incline. A homogeneous mixture of two materials, one rich in lime and theother rich in silica, is fed into the high endof the kiln. The kiln is continuously'rotated, causing thernixture to pass from'the high end of the kiln through the different zones of the kiln, know'n as the dehydration zone, the calcinating zone, and the clinkering zone. Heat is applied to the kiln as it rotates, to produce fusion of the mixture fed into the kiln in the form of a cement clinker.

' It is general practice to rotate the kiln by an electric motor coupled to a gear rim which surrounds the kiln. The electrical power for the motor is usually obtained froni'conventional power lines, although an electrical generator could be employed. In either case, occasional power failures are apt to 'occur.

A power failurewhich lasts a substantial length of time will not'only spoil the batch in" the kiln, but it may also necessitate a costly repair operation on the kiln. Once the kiln stops rotation, the kiln shell might Warp, being hot at bottom andcold on top. In some cases,

" the refractory brick liner on the interior cylindrical surface of the kiln is damaged and must also be replaced in order to place the kiln in working condition. It is one of the objects of the present invention to provide a drive mechanism for a rotary kiln using an electrical motor in which electrical power failures do not stop rotation of the kiln. I

If Eventually, even with normal operation of the kiln, the refractory brick liner within the kiln must be replaced. It is always a practice to replace the bricks on the bottom and lower portions of the kiln. Subsequently, the kiln is rotated and the other portions are lined. This is difficult with presently used kiln drive mechanisms, since they are free to rotate in either direction. It is, however, desirable 'under. certain conditions when replacing the refractory brick liner to rotate a kiln in the opposite direction to its normal operation, as will be explained hereinafter. It is-a further object of the present invention to provideadrive mechanism for a rotary kiln which is normally free to rotate only in one direction, and which may be adjusted to rotate in either direction.

.Further objects and advantages of the present invention will be apparent from a further reading of this disclosure, particularly when viewed in the light of the drawings, in which:

2,910,286 Ratented Qct. 27,. 1959 2 Figure 3 is a plan view, partly cut away and in section,- of the backstop mechanism illustrated in Figure 2; and Figure 4 is a front elevational view of the rotary kiln and drive mechanism illustrated in Figure 1. I

As illustrated in Figure 1, a rotary kiln is supported on suitable bearings 12, usually in an inclined position.

' Rotary kilns are generally from six to twelve feetor more Figure l is a schematic view of a rotary kiln and a drive in diameter and eighty to five hundred feet long. The kiln 10 is formed by a hollow cylinder 13, and is lined with a layer 14 of refractory bricks 15 which are disposed in abutting relationship. Since the use of rotary kilns'in the production of cement is well known and forms no part of the present invention, the details of the devices for charging the batch into the rotary kiln and discharging it from the kiln, as well as the details of the cement manufacturing process have'not' been specifically described. The kiln "10 is provided with an annular gear rim 16 which extends aboutthe periphery of the kiln 10 and is coupled to a drive mechanism 18.

The drive mechanism 18 obtains rotary energy from an electric motor 20 which is electrically connected to a power line, designated 22, which conducts electrical energy from'a generating plant to the electric motor in the conventional manner. The motor 20 is coupled to a first rotatable shaft 24 of a main speed reducing gear train 26 by a flexible couplerv 28. A first pinion gear 30 is secured to the first shaft 24, and this pinion gear 30 is meshed with a first spur. gear 32 which is secured to a second rotatable shaft 34 in the gear train 26. p 'A second pinion gear 36is also secured to the second shaft 34, and this pinion gear 36 is meshed with a secondspur gear 38 which is secured to a third rotatable shaft 40. Athird pinion gear 42 is secured to the thirdshaft 40 and meshed with a third spur gear-44 which is secured to a fourth rotatable shaft 46. The spur gear 44 is meshed with a direction reversing gear 48 which is secured to a fifth rotatable shaft 50. A pinion gear 52 is secured to the fifth shaft 50 and meshed with the gear rini 16 on the kiln10. M 1

There has been coupled a gasoline motor 54 to the speed reducing gear train 26, and hence to the kiln 10, in order to provide continuous rotation of the kiln 10 in the event of failure of the electric motor 20 to supply the requisite rotational power. The gasoline motor 54 is mechanically connected to the driven end of a second speed reducing gear train 56, and the driving end of the gear train 56 is connected mechanically to the driven end of a free-wheeling clutch 58. The driving end of the freewheeling clutch 58 is mechanically connected to the first shaft 24 of the gear train 26, thus coupling the gasoline motor 54 to the kiln 10.

The free-wheeling clutch 58 disengages the gasoline motor 54 from the kiln 10 as long as the angular velocity of the driving end of the clutch exceeds the angular velocity of the driven end of the clutch, the direction of rotation 'of the driving and driven ends ofthe freewheeling clutch being the same. However, if the electric motor 20 =fails to supply sufiicient energy, theangular velocity of the driving end of the free-wheeling clutch will fall below that of the driven end of the clutch, and power will be supplied by the gasoline motor 54 to the kiln 10. Since free-wheeling clutches of the type here described are well known, and the details of the particular free-wheeling clutch form no part of the present invention, these details have not been set forth.

A backstop mechanism 60 is connected to the second shaft 34 of the gear train 26 and prevents rotation of the kiln 10 in the direction opposite to the operating direction. The shaft 34 is secured within a hollow member 62 by a key 64 disposed within slots 66 and 68 in the shaft 34 and member, respectively. Theouter surface of the member .62, designated 70, is coaxial-with the shaft 34, and this surface 70 is provided with a plurality of indentations 72. Each of the indentations has a fiat surfaced trailing edge 74 and a flat surfaced leading edge 76, the direction of rotation being indicated by the arrow in Figure 2. The plane of each trailing edge forms an acute angle with the plane extending through the axis of the shaft 34 and the axis formed by the intersection of the trailing edge plane and the outer surface 70 of the hollow member 62, this angle being shown in dotted lines in Figure 2 and designated A. In like manner, an angle B is formed between the radial plane and the plane of the leading edge 76 of the indentations '72, this angle also being indicated by dotted lines in Figure 2 and being much greater than the angle A. It has been found that the trailing edge 74 of the indentations 72 must be steeper than the leading edges 76, and more specifically, angle A must be less than 45 degrees and angle B greater than 45 degrees for the backstop mechanism to function in its intended manner, as will be later apparent.

A roller assembly 78 is disposed about the outer surface 70 of the hollow member 62. The roller assembly has a plurality of roller bearings 80 disposed in a race 82, one roller 80 confronting each of the indentations '72 in the'outer surface '70 of the hollow member 62. The

race 82 has separation members 84 between adjacent rollers '80, the surfaces of the separation members 84 conforming with the surfaces of the rollers 80, and these separation members 84 are interconnected by links 86 which are pivotally connected between adjacent separation members 84 at each end of the rollers 80. 'The links 86 are also connected to fingers 88 by helical springs 90, and the fingers 88 are secured to a pair of annular bushings '92 which are coaxial with and secured to the hollow member 62. As a result of this construction, theroller bearings 80 rotate about the axis of the shaft 34 in positions which are limited to a range of movement, namely approximately the length of the indentation '72.

A cylindrical outer race-94 is disposed coaxially about the hollow member 62 and abuts the roller bearings 80. A brake shoe 96 surrounds the outer race 94, and a layer of brake lining '98 abuts the outer race 94 and the brake shoe 96. The brake shoe 96 is in the form of a strip disposed in a generally cylindrical shape with its ends 100 and 102 confronting each other but spaced from each other, as illustrated in Figure 2. A bracket 104 is attached 'to the brake shoe 96 adjacent to its end 100, and a second bracket 106 is attached to the brake shoe '96 adjacent to its other end 102. Both of the brackets 104 and 106 are provided with confronting apertures 108 and 110, respectively, and a shaft 112 extends through the two apertures 108 and 110, the portion 113 of the shaft disposed Within the aperture 110 being threaded and threadedly engaged with a nut 114 mounted to the bracket 106. A wheel 116 is secured to the shaft 112 on the opposite side of bracket 104 from the threaded portion 113 of theshaft 112, and a helical spring 118 surrounds the shaft 112 between the bracket 104 and the wheel 116 and abuts the Wheel 116 and bracket 104. i The brake shoe 96 is anchored to the support member for the speed reducing gear train 26, in the present instance the surface of the earth, to prevent rotation of the brake shoe 96. A pair of brackets 120 and 122 are mounted to the brake shoe 96 on the opposite side of the brackets 104 and 106, as shown in Figure 2, and a pair of arms 124 and 126 are secured to the brackets 120 and 122, respectively, at one end and to the supporting member, or earth, at the other end, as illustrated in Figure 1.

Since the electric motor revolves the first shaft 24 of the gear train 26-;at a more rapid rate than the gasoline motor 54 would through the speed reducing gear train 56, the kiln 10 is rotated entirely by the energy from the electric motor 20. If'electric power fails at any time during the processing of the batch, or the electric motor .20 fails for any reason, the free-wheeling clutch couples the gasoline motor 54 to the first shaft 24. The gasoline motor then is started and the kiln 1'0 continues to rotate, but at a slower rate than when driven by the electric motor 20. The rotation rate of the kiln 10 when driven by the gasoline motor 54, however, is sufficient to prevent damage to the kiln.

During normal operation ofthe kiln, the direction of rotation of the second shaft 34 of the gear train 26 is clockwise, as illustrated in Figure 2 by the arrow. The roller bearings under these conditions are revolving in the deepest portions of the indentations 72, since the rollers 80 tend to move down the leading edges 76 of the indentations 72. The brake shoe applies pressure to the outer race 94 as a result of the tension placed on the brake shoe by the shaft 112 and wheel 116; however, this tension is adjusted by positioning the wheel 116 to be insufficient to substantially retard rotation of the roller bearings 80' when the second shaft 34 is revolving in the forward direction. However any attempt to rotate the shaft 34 in the reverse direction, causes the roller bearings 80 tobecome wedged between the leading edges 76 of the indentations 72 and the outer race 94, thus preventing rotation of the hollow member 62 in the reverse direction. Sufficient tension is applied to the brake shoe 96 bythe lshaft 112 and wheel 116 to "completely stop rotation-of the roller bearings 80,under these conditions.

When the refractory brick liner 14 is to be replaced, workmen are able to continually work on the lower portions of the kiln, since the kiln '10' -rnaybe rotated in its normal operating direction, but resists rotation in the reverse direction regardless of the weight distribution in the kiln 10 because of the backstop mechanism 60. It is often desirable to reverse the rotation of the kiln 10 for a short angular distance when the liner 14 is being completed in the 1am. This is accomplished by merely releasing the tension on the brake shoe 96 by adjustment of the wheel 116, and hand positioning the kiln 10into the desired position.

From the foregoing disclosure, the man skilled in the art will readily devise many modifications and improvements upon the device herein set forth, including applications for the device inarts otherthan cement manufacturing. It is therefore intended that the scope of the present invention be not limited by the foregoing disclosure, butrather only by the appended claims.

The invention claimed is:

l. .A rotary kiln comprising a drum,,a brick liner disposed on the inner surface of the drum, means for rotatably mounting the drum at an incline to the horizontal, a drive mechanism mechanically coupled to the drum including a motor, and a backstop mechanism coupled to the kiln to prevent rotation of the kiln in the reverse direction including a shaft coupled to the first motor, a hollow member provided with indentations on its. outer surface secured coaxially about the shaft, a round bearing disposed adjacent to each indentation, an outer race disposed coaXia'Ily with the shaft and adjacent to the round bearings, and releasable braking means operatively associated with the outer race to prevent rotation thereof relative to the drive mechanism.

2. A rotary kiln comprising a support member, a drum rotatably mounted to the support member at an incline to the horizontal, a brick liner disposed on the inner surface of the drum, a drive mechanism mounted to the support member and mechanically coupled to the drum including a motor, and a backstop mechanism coupled to the kiln to prevent rotation of the kiln in the reverse direction, said backstop mechanism including a member coupled to the kiln provided with a cylindrical surface having indentations thereon, said indentations having steeper trailing edges than leading edges, a round bearing disposed adjacent to each indentation, an outer race disposed coaxially about the member and adjacent to the round bearings, a brake shoe disposed coaxially about the outer race and mounted to the support member, and means to apply and maintain tension on the brake shoe.

3. A drive mechanism for a rotary kiln comprising a support member, an electric motor mounted to the support member, a free-wheeling clutch having a driven and driving side, a first shaft connecting the electric motor to the; driving side of the free-wheeling clutch, a gasoline motor mounted to the support member, a first speed reducing gear train connected between the gasoline motor and the driven side of the free-wheeling clutch, said clutch coupling the gasoline motor to the first shaft only when the angular velocity applied to its driven side exceeds the angular velocity applied to its driving side and both angular velocities are in the same direction, a first pinion gear secured to the first shaft, a second shaft, a first spur gear secured to the second shaft and meshed with the first pinion gear, a backstop mechanism having a hollow member secured about the second shaft having a plurality of indentations at a common distance from the axis having trailing edges forming an angle no greater than 45 degrees with the radius from the axis of the member to the intersection of the trailing edge of the indentation and the outer edge of the member and leading edges forming an angle greater than 45 degrees with the radius from the axis of the member to the intersection of the leading edge of the indentation and the outer edge of the member, a first annular bearing race mounted coaxially with the hollow member, a round bearing disposed adjacent to each indentation in the hollow member and rotatably mounted in the first race, a second bearing race mounted coaxially with the first race and abutting the bearings mounted in the first race, a brake shoe disposed about the second race and mounted to the support member, said shoe having spaced confronting ends, a layer of brake lining disposed between the brake shoe and the second race, a pair of brackets secured to the brake shoe adjacent to the ends thereof, the first of said brackets having a threaded aperture therein and the second bracket having an aperture, a third shaft slidably disposed in the aperture in the second of the brackets and threadedly engaged in the aperture in the first bracket, a Wheel secured to the third shaft confronting the side of the first bracket opposite to the second bracket, and a spring disposed between the wheel and the first bracket.

4. A rotary kiln comprising a support member, a drum rotatably mounted to the support member at an incline to the horizontal, a brick liner disposed on the inner surface of the drum, a drive mechanism mounted to the support member and mechanically coupled to the drum including a motor, and a backstop mechanism coupled to the kiln to prevent rotation of the kiln in the reverse direction including a hollow member coupled to the kiln having a plurality of indentations at a common distance from the axis, the indentations having trailing edges forming an angle less than 45 with the radius from the axis of the member to the intersection of the trailing edge of the indentation and 'the'outer edges of the member and leading edges forming, an angle greater than 45 with the radius from the axis of the member to the intersection of the leading edge of the indentation and the outer edge of the member, a first angular bearing race mounted coaxially with the hollow member, a round bearing disposed adjacent to each indentation in the hollow member and rotatably mounted in the first race, a second bearing race mounted coaxially with the first race and abutting the bearings mounted in the first race, a brake shoe disposed about the second race and mounted to the support member, said shoe having spaced confronting ends, a layer of brake lining disposed between the brake shoe and the second race, a pair of brackets secured to the brake shoe adjacent to the ends thereof, the first of said brackets having a threaded aperture therein and the second bracket having an aperture, a shaft slidably disposed in the aperture in the second of the brackets and threadedly engaged in the aperture in the first bracket, a wheel secured to the shaft confronting the side of the first bracket opposite to the second bracket, and a spring disposed between the wheel and the first bracket. 

